As a filling material used in the dentistry, a dental amalgam which is prepared by mixing a dental amalgam alloy powder and mercury has hitherto been mainly employed. However, since this dental amalgam uses mercury which is harmful to human bodies and likely causing an environmental pollution, in recent years a dental composite resin composition has become widely used as a replacement of the dental amalgam, in view of the safety.
Such a dental composite resin composition is generally composed of a polymerizable monomer, an inorganic filler and/or an organic filler, a polymerization catalyst, a pigment, and a stabilizer and is usually in the form of two types of pastes in which one paste is incorporated with peroxide and the other paste is incorporated with amines or sulfinic acids. These two pastes are mixed at the time of use and then polymerized.
This dental composite resin composition is generally c-assified, depending upon the type of the filler used, into a conventional type composite resin having an irregular particle sized filler of about 1.about.50 .mu.m, such as silica, quartz, barium glass, lithium aluminum silicate, and ceramics, and a MFR (microparticle filled resin) type composite resin having superfine sized silica filler of 0.005.about.0.04 .mu.m.
However, the above-described dental composite resin composition has such a drawback in abrasion resistance that its cured material is readily abraded by mastication of foods as compared with the dental amalgam. In particular, the cured conventional type composite resin composition has a drawback that after abrasion in an oral cavity, its surface becomes rough. In order to solve such a drawback that the surface becomes rough, MFR has been developed, but its abrasion resistance is rather reduced. Further, while the X-ray contrast is a very useful property in diagnosis by a dentist, when a compound such as barium, lead, tungsten, or zirconium is added as a X-ray contrast medium to the dental composite resin composition, the mechanical properties are decreased and the color tone is deteriorated, and hence, it is difficult to impart a satisfactory X-ray contrast.
In order to overcome the drawbacks of the above-described dental composite resin composition, the present inventors have made extensive investigations and found that it is effective to add a platinum-color element powder and/or a platinum-color alloy powder to the dental composite resin composition.